Friday, January 18, 2008

Math: If it takes 5 window washers 7 hours to clean a business building then how long will it take 4? -

Stupid math problems! GAH! If it takes 5 window washers 7 hours to clean a business building, then how long will it take only 4 window washers to clean the same business building?

1 window washer needs (5 *7)= 35 hours 4 window washer need 35/4 = 8 3/4 hours

Create a proportion. Proportions represent a relationship between two numbers. The relationship between the window washers and hours to clean the building is 5/7. Set this equal to 4/x to determine how many hours it will take 4 windows washers to clean the building. Then cross multiply to solve for x! 5/7 = 4/x 5x = 7 * 4 5x = 28 5x/5 = 28/5 x = 5.6 hours to convert .6 to minutes: 6/10 of an hour 60 minutes/10 = 6 and 6 * 6 = 36 So the answer is 5 hours and 36 minutes

make a proportion. do 5 over 7. and then 4 over x. then cross mulitply and divide. like this: 5/7 = 4/x 7(4) = 28 28/5= 5.6 5 hours and 40 minutes. proportions work for almost anything!!

5/7 = 4/x 5x=28 x=5.6 hours .6 hours =36 minutes so 5 hours, thirty-six minutes

It takes 35 washer-hours to clean one building. It takes 35/4 washer-hours for 4 washers to do the job.

its reverse proportion it will take 8.75 hours for 4 of them just devide 5 by four and multiply by 7

well, the key here is to get a constant rate: 5/7 = 4/x. then solve for x: x= 28/5

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